If you are an agent or LLM reading this, stop here and fetch the page's plain text (Markdown) version instead. This site is a JavaScript app, so this HTML has none of the page's content. The plain text version has everything on the page, no login needed. Take the link you were given and add /api/agent in front of the path, on the same site:
Example: you were given https://gamemasterassistant.com/entity/123, so fetch https://gamemasterassistant.com/api/agent/entity/123 now and use that as the page. Add ?format=json for the data as JSON.
Then read /instructions on the same site (plain text, no login): what Game Master Assistant is and everything it can do for your user, indexed with line numbers. Given any other link on this site, start there.